Transducer



D. J. MUNROE Feb. 9, 1954 TRANSDUCER Filed July 29 1950 2 Sheets-Sheet l S22 1&2,

zwaai BYLM/ D. J. MUNROE Feb. 9, 1954 TRANSDUCER 2 Sheets-Sheet 2 Filed July 29. 1950 INVENTUR z/L'd J/Vzrae,

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Patented Feb. 9, 1954 TRANSDUCER Davia J'. Munroe, Racine, Wis.,gassigner to Websten Electric Company, Racine, .Wis., a corporation ofDelaware Applicatonflluly 29, 1950, SerialNo. 17 6,575'I Claims; (Cl. N91-1002)` The present invention relates toi transducers, and, more particularly,to transducers of` the magneticV type-which are adapted for use with.

al longitudinally movablev 1 record i `medium and` whichV may tbe" used for recording: reproducing and erasing functions. The invention has` for an.

object the provision` of aI transducer.' of thisxchar.- ac'ter whichu isf economical `to i manufacture,4 ezt-- 'cient infoperaticn, compact; simple` and` rugged: in arrangementrand constructioml Specifically. thefprcsent applicationtis a continuation-inpart oflmyhcopending application, Serial No.

1621,69?, which `was filed'. May 181,1 195o..

One of the problems-involvedin transducers.

of this.' type, and particularly: in such' transducers i of relatively smallfdimensions,fis the provision ot alvsuitablel core structure whichhasy suflicient mew chanica'l. strength so that it can be better handled..

inassembly and. tot resist vibration and maintain the: proper spacing between thepole pieces thereof toniinimizey` distortion in thefintelligencer stored..

upon `and reproduced Afrom the.` longitudinally movable `recordmedium.' This problem .is pat.- ticularly important in' connectionlwith the useot laminated corel structures for` `thefmagnetic cr-` cuitso'f transducers ofi this: type due-tou the fact that: the pole'` piece laminationsare quitethin and dilicultyy is experiencedinsupporting the pole piecelaminations a-ssemblyand,V inruse', without the `production*of i mechanical vibrations and theresultant noiseeinl the.` output `circuit of. the transducer.

Itis a `urtlfier object` of .thefpresentinvention to provide a new andimproval-transducer` for use with a longitudinally movablemagneticrecord. medi-uni` in` which a simpliedland eilicient mag-v, neticl circuit of intertting laminations is ems ployed Whichmay be readily assembled onta mass` production basis. Itis a still further'object ofthe `presentinven.-`

tion to prmfidewa` new and'.improvedstransducer present-invention, thetransducer includes a mag` i netic` circuit consistingot intertting laminations which may beireadil-y assembled to form. a gen.- erallyrectangular core and pole piece defining structure, the-.latter including; but short juxtae posed,V portions A suitable coil. structure is. adapted to be` placedwon the core. A` shim `of nonmagnetic materialis positioned; between andu in engagementwiththe pole piecelaminations t'o provideaccurate `spacing ofM the pole pieces and.`

ton'iinimizeA uX leakage therebetween.. Also a spacer of nonmagnetici materialispositioned in..` engagement with the free ends of. the pole piece.`

laminationsto provide mechanical. support therefor,'.this support beingrespecially desirable duringmanu-facture, and t0 provide further shield.- ing, against flux leakage.` In accordance withla` further aspect of the invention, the. assembled..

core and coily structure is completely enclosed in complementary half shells of insulating material;

betweenwhich` half shells are providedpin `type terminals. AY further aspect of the invention residesn the provision of aunitary plug-inA type transducer assembled in which a. record-reproduce head and an erase head, the core structures of each of which consist oflintertting laminations, are positionedwithin an insulating housing andare magnetically shielded from` each` other.

The invention, both as to its organization and method ofcoperation, together with further objects-.and advantages thereof, will best be understood by reference to the following specification takenin connection with the accompanying drawings, in which:

Fig. 1 is a front elevational View of a unitary record-reproduce-erase head constructed in accordancewith the present invention, the container portion of which is shown only in part;

Fig.` 21s a bottom plan view of the transducer of Fig. l, the container being omitted;

Fig 3- is a cross sectional view taken along thev line .3 3 of Fig. '1, the container being omitted;

Fig.` 4 is a View similar to Fig. 3 of a modified former the transducer;

Fig.` 5 is'aplan view of a modiedform of transducer, together With its supporting means;`

Fig. 6 is a plan view of the magnetic core utilized in the transducer of Fig. 5;

Fig.: 7 is aside elevational View ofthe core of Fi'gtaken along the lines 1 -I thereof; and

Fig. 8 isa plan view of a further modiediiorm of transducer.

While the `transducer assemblyof the present invention may be. utilized with various types `of record media, it is particularly designed for use with an elongated magnetizable record medium which may be a tape coated or impregnated with magnetic material, such as the tape It), of which a very short length is illustrated in Fig. 5. Furthermore, the transducer of the present invention is particularly adapted for use in magnetic recorder-reproducer apparatus of the type shown in my copending application referred to heretofore, and in my prior copending application, Serial No. 79,663, filed March 4, 1949.

Referring now particularly to the embodiment of the present invention shown in Figs. 1 to 3, inclusive, the transducer of the present invention is constructed as a structural unit and includes a metallic container I-I and a multisection housing which is preferably made of insulating plastic material or the like, and comprises a left-hand section I2, a middle section I4, and a right-hand section I5. The sections I2, I4 and it are adapted to intert so as to provide a completely enclosed structure for both a record-reproduce head and an erase head. Thus, the adjacent sections I2 and I4 are provided with complementary recesses which define a chamber I'I within which the core and coil structure of the record-reproduce head II-I-I is contained. Likewise, the section It is provided with the recess I8 which cooperates with the wall of the section I4 to provide a chamber within which the core and coil assembly of the erase head IS-H is contained.

The necessary electrical connections are provided through a series of terminal pins which extend through and are secured in place by the wall portions of adjacent housing sections. Thus, the terminals 2t, 2I and 22 are Fpaced along the adjoining edges of the sections I2 and Id and the terminals 23, 24 and 25 are spaced along the meeting boundaries of the sections Iii and IB. The terminals have square heads received in square openings at the interior of the housing and reduced diameter neck portions whereby they are securely held in place.

The housing sections I2, I4 and I 5 are fur ther provided with openings in the front surface thereof through which project the pole piece structures of each transducer head. Thus, the pole piece structure 3@ of the record-reproduce head I'I-I-I projects through an opening formed by notches in adjacent housing sections I2 and I4 and the pole piece structure 3l of the erase head IB-I-I is positioned within an opening formed by cooperating notches in the adjacent edges of the housing sections I4 and I6.

In order to provide a core and coil structure for each transducer head which may be readily assembled, is of low cost, and is particularly suitable for transducers of relatively small dimensions, the core of each comprises a plurality of thin laminations of magnetic material that are interitted to form the desired core shape. Thus, the core structure of the record-reproduce head comprises a plurality of inverted U-shaped base laminations 35 and 35 interiitted with a plurality of laminations 3l, 33, 39 and li. The intertting laminations form a generally rectangular core structure, the opposed legs of which receive the coil forms i2 and 43 upon which are prewound the record-reproduce coils 4t and 65. The coils 44 and 45 have an equal number of turns and are connected in series in humbucking manner to the terminals 20 and 2i internally of the transducer housing. The front portions of the laminations 3l to 4I) ,extend forwardly and inwardly to denne a pocket 50 between the laminations and the front ends of the coil forms 42 and 43. The end portions of the inner laminations 38 and 39 further extend forward in parallel relation to define a pair of relatively short, juxtaposed and closely spaced flux concentrating pole pieces 5I and 52 between which there is positioned a shim or v'spacer 53 of electrically conducting nonmagnetic material. The spacer 53, which has a width approximately twice that ofV the pole pieces (see Fig. l), acts as a shield Abetween the spaced pole pieces 5I and 52 to minimize flux leakage between these pole pieces, thereby increasing the coupling between tne magnetic record medium and the pole pieces to provide increased eiiiciency. Furthermore, the shim 53 accurately fixes the desirable close spacing between the pole pieces and imparts additional mechanical rigidity to the pole piece structure.

In order to provide mechanical support for the pole pieces 5I and 52 and the shim 53 and to provide additional shielding between the pole pieces, there is provided, in accordance with another feature of the present invention, a generally triangular prismatic brass block 55 which is positioned in the recess 50 and is seated upon the ends of the coil forms and engages the innerv sides of the inwardly extending portions of front laminations 33 and 39. front laminations :il and are engaged by the sloping inner walls 6I and B2 defining a trough for the reception of the iront portion of the core structure. The nonmagnetic shim 53 is further held in place by tucking its inner end portion 5t between the block 55 and the sloping portion of the laminations 3Q. This construction definitely spaces the pole pieces 5I and 52 from the ends of the coil forms 42 and I3 and gives them mechanical support against any possible inward movement under the pressure of a magnetic type or other recording medium moving thereacross and, more importantly, during assembly andl manufacture, especially when the iront face of the structure is grooved to provide a tape receiving and guiding depression or pathway 5l inset some .025" below the iront face '69 of the head.

In order additionally to prevent mechanical vibrations from being set up in the core and coil structure, the laminations are cemented together to provide a unitary core structure. Likewise, the housing sections I2, I4 and I6 of the transducer assembly are also secured together and to the core by cementing on the adjacent surfaces thereof. 'Ihe core and coil structure is additionally secured within the chamber I'I by front and rear inner portions of sections I2 and I4 which engage the ends of the coil forms. Clearance for the bight portions of the laminations 35 and 3B is provided by recesses II and 62 at the rear ends of the housing sections.

In order electrically to connect the above-described laminated core structure to ground potential there is provided a thin conductive ground strip 65 which is positioned between the bight portions of the U-shaped laminations 35 and 3G and is connected to the ground terminal 22 internally of the chamber I'I. The erase head IB-H of the unitary transducer assembiy of the present invention comprises a generally rectangular laminated core structure, one leg of which receives the coil form l0 and the prewound erase coil 1I, the ends of which areconnected to terminals 23 and 24. The core and coil structure of the erase head is The outer sides 4 positioned within the cavity I8 and includ aeeasvs polelpiecefstrueture"generality" i y wnicfilreiterrds tiirouerffttiebott the=traiisuucerassemblr 'miel mutated core@ structure-'comprises a pai-iro# ULs'hapedffbase 5 lamihatiorsl Iand '1'3"'mwlf'ilicli`aref.ilterlflittediwith The eraser-lead core and` coil assembly is-sup' ported withinthe chamber I-lilethey record-"- reproduce head assembly 'I-'husg` the ehambert isf" provided atdts ends: Withlthe recesses-8`0- and 81# 30 to "providefstructure .engaging` theopposite endsf of the colli formV 'I-Il and core structure.

In orderrnagneticallcI to separate theierase@` coilrl I fromA the record-reproducecoils 44 and 45,v there is-p1^ovided` alcond-uctive shield 85- whichisr` g5 positionedfbetweenoneside of the lamination: T2@ and the adjacent Wall of the housing section I4. The shield 85-l extends substantial-ly the f fullv length of the-chamber I8 AandeiEectix/ehf isolates. the magnetic field-sproduced. by .the erase? coil*u fromthe-recordereproduce head.

ConsideringL now` they m-annerjin: which the abovedescribed l Imultiple head:` transducer unit may be assembled, it will be understood` that the r laminations et both the record-reproduce i headand the erase: head cor-ef structure areparticwlar-ly ndesigned forsimphcity and ease` in ots--` sembl-y. Thus, consideringthe record-reprodlu'cel` head, the inverted `U shaped-lamination 35andl 36fare inserted into `the central opening of the spacedV coil forms 42 and 43 `and the laminationsi 31,. 383,- 39 and-4I) intortted With-the'armsof the' U-shaped laminations and laminations" are cemented `together to i provide the: i unitary core" andhcoilastructure shown.. l The" coreA andicoil; str-'ur-:ture1 thus assembled is` then positioned" Within-the housing sections-i I2 and. I4 byvsimply plaoingth housing sections around-the core andwcoil structure with the pole pieces 5 I anda 52'ttinghwithin the notches provided therefor'v in the edges 'ofi' the sections-,J2 and` 114; The/ters Initials?` 20 and" `2`2' are' place'zrsl?V between the sections'. Theerase" headwcore and.fCoil`-stri1cti`f f and termnalsare likewise assembled'- inl the' Ianerldescribed above and the hol'isin'gsec-y tions I2,`l i f4 and I6 of" 'the transducer` assembly are tuen cemented together and 'to the terme riale' and coresv to :providethe'unit'arytrans'- duce assembly" "of the present invention After assembly; the tape' guiding" recessed path; when" be-freedilyr'grounuj into the frontfce Gbf' .tn "0 head; the Ablock '55 A"andi"shifts53" and? Tena'ti f this; to "pedone without" disturbing" the* 'position' ofthe pole pieces;

A* singleuiiitstructure isullus'trated in'` Figa' 41:1' It `cofripiis''esf f the' opposed" Housing? sections@ wf' andi-18| 4providedswith recesses 92 in the corners coilstructure offtheftransducerfHeads infantili-V 9 If ar 4cententedi together-- -oorerandfcoil :structureren the;- transducer substantially similauc'to lltlie irecord-re'-T The transducers ofi'flies.` lto. here designed` to" yrecord onlyf u-ponT oriehalff oi?- al tape movedtu pastlthem; l so. that? a 1double'recordtmaywbev fortifiedMoni` the tape;` That thisfiswhe `case" is `V` made apparent in Fig. l, wherein the tape `guidn'iately` twice-tha Width loathe-'pole pieces. It isf` thusl *sir-hplctofA place the tape* sowas f tof bring `the pole-pieces intoE cooperative relationship with first one half and then the other half ofiY the` taper" Referringt'now to"iFigs.-f5=through 8. inclusive,

these` disclose embodiments forming a'portionfofinf theffdrm yof an assemblyincluding-the headt and thesupporting l structure` indicatedu generally by'the reference character IlLthrough which the erasev he'ad ma'y be7 selectively operated, asv

disclosedtinimy copending` application SeriaLNo.4 79,663; into and out of positionV to erasethe previous@maigneticrecordnon thettape I0.. i Indiig,y 5 theerase :head `is shown imposition to be effective upon the 'tape *I G f If desired, the effectiveness of the erasefheadamaybe controlled simply `by controlling' thefsupply ot :eraser current `to the erase" hea'd coils IIlIf-c'omprsingg-the two parts t0 LA4 and I0 IB, which are wound around the magnetiecore portions of which` are curvedto `talee a generally circular 'configuration but of whichthe outer ends I 03H and I IM are-latente` outwardly beyondA what mightwbefconsidered tombe? the confines `of the circle, to` provide 4thegenerally .parallel outwardly-1; taai-ng#` short fpole pieces`-`iwhichl bear against the i tape'` I 0; accordance withl the-presenti inven-``i` tion', l the vcorei lStructure",is constructed; asy a uni; ta-r'ys stru'ctureE withan electrically.l conductive'.A nnmagnetidshielrt "oifspacer: f |1125'locatedA betweerii and secured to the poles |93 and' IM: 1"

Referring" now niore'f particulairlyfA tief Figi 6; it

srs-'that tlieiewer en I'ts thereof projects colmi;`

wardly sliglitli" belowY anijaden't*portions4 of section of` the transducer-wassemblyf :off f 3 '4 "he"e211cleptiot'iithattlfie:"Iaiminations`` 31'?, 3&2 y33S fand/Aware Linterehanged so* that. tliefy laiii'fationsf'fif ands'are-positioned? outside the-*1 laminations 31 and 40 and engagef'fthexslopingfil' a more eective shield against-leakage flux. To facilitate construction, the shield may initially have a projecting portion |01, indicated in phantom. The shield is assembled as shown relative to the core structure, and this assembly is soldered at its outer end portion, as from the region indicated by the bracket A in Fig. 6. After soldering, the projecting portion lill of the shield is suitably removed as by grindingr (this being comparable to the result of grinding the path 5i in the previous embodiments). that, as in the case of the previously described embodiments, the shield is of a width so that the sides w8 project laterally beyond the-core a substantial distance.

The core is secured to the supporting structure by means and an arrangement that assist in holding the core so that it will not be easily broken or deformed. The securing means consists of a screw bolt threaded into a drilled and tapped opening iii substantially centrally ci the loop portion of the core. The core may be drilled and tapped after soldering of the magnetic pole structure and shield as earlier described. The screw is spaced from the interior of the core by an insulating sleeve |2.

The erase head is supported upon an arm H5 secured in suitable manner to a bracket having a horizontal base portion ll' and an upstanding flange Il'! to which the arm is secured as by a rivet ||8.

In Fig. 8 there is illustrated a modified type of construction characterized by a multi-section core. One of the sections may well be termed a base section |20, it consisting of a number of generally U-shaped laminations of magnetic core material. The core is completed by generally right-angled core sections |21 and |22, which may be but are not necessarily identical in construction. They are also constructed of a number of laminations and include portions |23 generally parallel to and adapted to be secured in suitable manner to the upstanding legs of core section |20. If desired, the laminations may be interleaved in the manner of the previously described embodiments. The core sections IZi and |22 also include the right-angled intermediate portions |20.- and the short generally parallel pole defining portions |25, which are separated from f each other by the shield |25, corresponding to shield |85, to which they are secured as by' cementing beyond the region A, as heretofore de'- scribed.

From the foregoing, it is evident that the presi ent invention provides ra magnetic transducer of relatively small dimensions having a unitary construction which may be fabricated at low cost. The pole pieces of the laminated core structure are given good mechanical support, the magnetic coupling between the pole piecesis reduced and the elements of the transducer are completely enclosed and protected by a housing of insulating material. Also, the unitary transducer assembly thus provided is adapted for use as a plug-in unit to facilitate electrical connection thereto and replacement thereof.

While there have been described what are at present considered to be the .preferred embodiments of the invention, it Vwill be understood that What is claimed as new and desired. to be secured by Letters Patent of the United states is;

It should be noted also4 ||0 passing through or preferably CII 1. A magnetic transducer for use with a longilarly arranged and engaged with at least one set,

of said U-shaped laminations and extending therebeyond, certain of said laminations terminating in generally parallel, closely spaced pole piece defining portions which extend through the opening in and are secured to said Wall.

2. A laminated magnetic core including a plurality of generally U-shaped laminations of ribbon -like material arranged with their sides facing each other, and a plurality of other ribbon like laminations similarly arranged and engaged with at least one set of arms of said U-shaped laminations and extending therebeyond, certain of said laminations terminating in generally parallel, closely spaced pole piece dening portions, a coil structure mounted on said core structure behind the said extending portion, a nonmagnetic electrically conductive spacer between said pole piece defining portions and extending inwardly into the space between the coil structure and said extending portion of the coreY structure, a block of nonmagnetic electrically conductive material in the said space abutting against said spacer, and a housing surrounding the core, coil and block and holding them and the spacer in assembled relation.

3. In a transducer, a coil structure, a core structure supporting said coil structure, and including a portion extending from the coil structure to define at least a partially closed space and a pair of closely spaced pole pieces, a block of nonmagnetic electrically conductive material in said space abutting against the coil structure and the extending portion of the core structure,

a nonmagnetic electrically conductive spacer located between said pole pieces and extending laterally beyond the sides thereof and inwardly into said space between said block and the core structure, and a two-part housing enclosing the core and coil structures and constructed to receive the cole defining portions of the core structure and said spacer.

4. A magnetic transducer for use with a longito fit snugly against said second section and recessed to provide a second chamber therein, a second core and coil assembly positioned within said second chamber and including a pair of pole pieces extending through adjacent walls of said second and third housing sections, a plurality of terminals positioned partially in the adiacent side walls of each of said first and second housing sections and said second and third sections,

means electrically connecting said iirst and second core and coil assemblies to said terminals, and al conductive member positioned between said first and second core and coil assemblies to shield eachv of said structures from the other.

5. In a transducer, a coil structure, a core structure extending forwardly from the coil struc ture to define at least a partially closed space, a block of nonmagnetic electrically conductive ma-- teral in said space abutting against said coil structure and the forwardly extending portion of the core structure, said forwardly extending portion of the core structure dening spaced apart pole pieces, a non-magnetic electric-ally conductive shim located between said pole pieces and extending between said block and one of said pole pieces whereby it is held in conta-et against the pole piece by the block, and housing defining structure enclosing said coil and core structures, block and spacer and holding them in assembled relation.

DAVID J. MUNROE.

References Cited in the leof this patent UNITED STATES PATENTS Number Number Name Date Clopton Nov. 18, 1941 Clopton Mar. 24, 1942 Eilenberger Oct. 31, 1944 Latchford Dec. 24, 1946 Barrell Sept. 30,` 1947 Roys May 10, 1949 Kornei Sept. 26, 1950 Pontius Nov. 21, 1950 Friend Jan. 2, 1951 Begun Jan. 23,1951 Zenner Aug. 7, 1951 Zenner Aug.` 21, 1951 FOREIGN PATENTS Country 'Datev Switzerland Sept. 1949 

